CHAPTER 11 A/D CONVERTER
User’s Manual U12688EJ4V0UM00
345
11.8 Operating Precautions
11.8.1 Stopping conversion operation
When 0 is written to the CE bit of the ADM0 register during a conversion operation, the conversion operation stops
and the conversion results are not stored in the ADCRn register (n = 0 to 7).
11.8.2 External/timer trigger interval
Set the interval (input time interval) of the trigger in the external or timer trigger mode longer than the conversion
time specified by the FR2 to FR0 bits of the ADM1 register.
(1) When interval = 0
When several triggers are input simultaneously, the analog input with the smaller ANIn pin number is
converted. The other trigger signals input simultaneously are ignored, and the number of trigger inputs is not
counted. Therefore, the generation of interrupts and storage of results in the ADCRn register will become
abnormal (n = 0 to 7).
(2) When 0 < interval
≤≤≤≤
conversion operation time
When the timer trigger is input during a conversion operation, the conversion operation stops and the
conversion starts according to the last timer trigger input.
When a conversion operation stops, the conversion results are not stored in the ADCRn register. However,
the number of trigger inputs is counted, and when the interrupt is generated, the value at which conversion
ended is stored in the ADCRn register.
11.8.3 Operation of standby mode
(1) HALT mode
The A/D conversion operation continues. When released by the NMI input, the ADM0 and ADM1 registers
and ADCRn register hold the value (n = 0 to 7).
(2) IDLE mode, STOP mode
As clock supply to the A/D converter is stopped, no conversion operations are performed. When these modes
are released using the NMI input, the ADM0 and ADM1 registers and the ADCRn register hold the value.
However, when the IDLE and software STOP modes are set during a conversion operation, the conversion
operation stops. At this time, if released using the NMI input, the conversion operation resumes, but the
conversion result written to the ADCRn register will become undefined.
In the IDLE and software STOP modes, operation of the comparator is also stopped to reduce the power
consumption, and to further reduce current consumption, set the voltage of the AV
REF
to V
SS
.
11.8.4 Compare match interrupt when in timer trigger mode
The compare register’s match interrupt becomes an A/D conversion start trigger and starts the conversion
operation. When this happens, the compare register’s match interrupt functions even if it is a compare register match
interrupt directed to the CPU. In order to prevent match interrupts from the compare register being directed to the
CPU, disable interrupts by the interrupt mask bits (P11MK0 to P11MK3) of the interrupt control register (P11IC0 to
P11IC3).
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